For a simple, brown tuber, potatoes have a long and storied history. Ancient Incans worshipped them; the Irish blamed them for a famine. Today, they are the fourth largest food crop in the world. Now, scientists have shed new light on just where these tubers came from. A genetic study shows that modern potatoes were cultivated from two wild ancestors, contradicting the straightforward story that has long been told.
Potatoes haven't always been smooth and tasty. Their ancestors, which still grow in South America, resemble gnarly fingers, and their bitterness makes them unappetizing, whether baked, mashed, or fried. Two subspecies of these wild spuds, one found in Chile, the other in the Andean highlands of Peru, look very similar but differ genetically. Most scientists have long assumed that European potatoes, the foundation for all modern cultivated potatoes, come from the Chilean variety, because Chilean lowlands resemble Europe's environment most closely. But between the Americas and Europe, in potato history, lie the Canary Islands, off northwest Africa. Shipping records from 1567 make these islands the first known home to potatoes outside of Central and South America. And some researchers say the potatoes there resemble the Andean variety but have never had genetic proof.
So David Spooner, a horticulturist with the U.S. Department of Agriculture and a researcher at the University of Wisconsin, Madison, decided to analyze those island spuds, making the assumption that whatever variety of potato grows there must be the kind that first traveled toward Europe. He found that some potatoes on the Canary Islands had genetic markers of Andean origins and some had markers indicating Chilean roots. "The idea that it was a single introduction from Chile just doesn't stand up," he says. Spooner speculates that different varieties could have been brought from South America at various times. Modern potatoes, he concludes, are a combination of the two ancestral species. Next, he hopes to analyze modern potatoes from other places, such as Europe and Africa, to tell a more complete story of the history of the potato. The results appear in the current issue of Crop Science.
Beyond illuminating the past, understanding the origins of potatoes can help scientists move into the future, says University of Utah botanist Lynn Bohs. "If we know what genes or ancestral species are involved in the evolution of the modern potato, we may be able to pull out useful traits," she says, "and make a better potato."